title: Evaluation of new in vitro efficacy test for antimicrobial surface activity reflecting UK hospital conditions.
abstract: BACKGROUND
  Antimicrobial surfaces aim to reduce microbial bioburden and improve hygiene. The current antimicrobial surface efficacy test (ISO22196) is an initial screening test but its conditions, high temperature (37°C) and relative humidity (RH) (100%) bear little relationship to in-use conditions.
  
  
  OBJECTIVE
  To develop an antimicrobial surface efficacy test providing a realistic second-tier test, simulating in-use conditions.
  
  
  METHODS
  Surface relative humidity, temperature and soiling were measured over one year at a UK hospital, enabling realistic parameters to be set for our surface efficacy test. A nebulizer, connected to a cascade impactor, aerosolized and uniformly deposited a Staphylococcus aureus suspension over test copper alloys and control stainless steel surfaces. Bacteria were enumerated following nebulization, and after a range of contact times, under [20°C, 50% RH] and [20°C, 40% RH] parameters reflecting in-use conditions; [37°C, 100% RH] was employed to reflect conditions used in ISO22196.
  
  
  RESULTS
  All copper alloys produced a >4 log10 reduction after 24h under all conditions tested. Copper alloys were more effective at [37°C, 100% RH] showing a >4 log10 reduction after 30 min than at in-use conditions [20°C, 50% RH and 20°C, 40% RH], for which 60 min was required to achieve the same level of kill, for most but not all alloys.
  
  
  CONCLUSIONS
  The use of the nebulizer to deposit bacterial inocula on surfaces showed little variability in results. Our method was more discriminatory than the ISO22196 enabling distinction between the bactericidal surface activity, which allows for a more rigorous selection of antimicrobial surfaces for potential use in healthcare settings.
authors.affiliation: Cardiff School of Pharmacy and Pharmaceutical Sciences, Cardiff University, Cardiff, UK.
authors.forename: M
authors.initials: M
authors.lastname: Ojeil
authors.forename: C
authors.initials: C
authors.lastname: Jermann
authors.forename: J
authors.initials: J
authors.lastname: Holah
authors.forename: S P
authors.initials: SP
authors.lastname: Denyer
authors.forename: J-Y
authors.initials: JY
authors.lastname: Maillard
mesh_terms: D000890:Anti-Infective Agents / Q000494:pharmacology*; D058491:Bacterial Load; D003300:Copper / Q000494:pharmacology; D004203:Disinfection / Q000379:methods*; D004783:Environmental Microbiology; D006761:Hospitals; D006801:Humans; D050296:Microbial Viability / Q000187:drug effects; D008828:Microbiological Techniques / Q000379:methods*; D013211:Staphylococcus aureus / Q000187:drug effects; D013499:Surface Properties; D006113:United Kingdom
chemical_list: D000890:Anti-Infective Agents; D003300:Copper
keywords: Antimicrobial surfaces; Copper; Microbial aerosols; Relative humidity; Temperature